Conventionally, as such spectroscopic light sources, deuterium lamps disclosed in Patent Document 1 and Patent Document 2 have been known. These deuterium lamps disclosed in Patent Document 1 and Patent Document 2 have light exit windows and are each arranged at a position where it becomes possible to emit light into a vacuum chamber of a mounting object (such as a spectroscope) via the light exit window. At this time, the deuterium lamp is fixed to a fixing portion provided on an outer wall or the like of the vacuum chamber whose inside is maintained in a vacuum state. For example, the deuterium lamp disclosed in Patent Document 1 comprises not only an anode and a cathode that generate an electric discharge but also a sealed container that stores the anode and cathode. The sealed container comprises a tube body and a cylindrical guide portion extending in a direction orthogonal to a center axis (tube axis) of this tube body that is an emitting direction of a discharge light. At the front end of the guide portion, a light exit window is provided. The guide portion is provided with an annular concave groove to be attached with an O-ring on its outer periphery surface. As a result of this guide portion of the deuterium lamp being fitted into the cylindrical fixing portion (an opening portion provided in the outer wall of the vacuum chamber), the deuterium lamp itself is attached to the mounting object, while the inside of the vacuum chamber of the mounting object is maintained in a vacuum state by being sealed airtight with the O-ring.
On the other hand, the deuterium lamp described in Patent Document 2 comprises not only an anode and a cathode but also a sealed container (tube body) that houses the anode and cathode. In addition, a light exit window is formed on one end side of the sealed container. A mouth ring is provided at one end of the sealed container, and this mount ring fixes the deuterium lamp described in Patent Document 2 to the fixing portion on the outer wall of the vacuum chamber of the mounting object.    [Patent Document 1] Japanese Utility Model Application Laid-Open No. S54-156976    [Patent Document 2] Japanese Patent Application Laid-Open No. H06-215734